Apparatus and method for depositing materials onto microelectronic workpieces

ABSTRACT

Reactors for vapor deposition of materials onto a microelectronic workpiece, systems that include such reactors, and methods for depositing materials onto microelectronic workpieces. In one embodiment, a reactor for vapor deposition of a material comprises a reaction chamber and a gas distributor. The reaction chamber can include an inlet and an outlet. The gas distributor is positioned in the reaction chamber. The gas distributor has a compartment coupled to the inlet to receive a gas flow and a distributor plate including a first surface facing the compartment, a second surface facing the reaction chamber, and a plurality of passageways. The passageways extend through the distributor plate from the first surface to the second surface. Additionally, at least one of the passageways has at least a partially occluded flow path through the plate. For example, the occluded passageway can be canted at an oblique angle relative to the first surface of the distributor plate so that gas flowing through the canted passageway changes direction as it passes through the distributor plate.

TECHNICAL FIELD

The present invention is related to the field of thin film deposition inthe manufacturing of micro-devices.

BACKGROUND

Thin film deposition techniques are widely used in the manufacturing ofmicroelectronic devices to form a coating on a workpiece that closelyconforms to the surface topography. The size of the individualcomponents in the devices is constantly decreasing, and the number oflayers in the devices is increasing. As a result, the density ofcomponents and the aspect ratios of depressions (e.g., the ratio of thedepth to the size of the opening) is increasing. The size of workpiecesis also increasing to provide more real estate for forming more dies(i.e., chips) on a single workpiece. Many fabricators, for example, aretransitioning from 200 mm to 300 mm workpieces, and even largerworkpieces will likely be used in the future. Thin film depositiontechniques accordingly strive to produce highly uniform conformal layersthat cover the sidewalls, bottoms and corners in deep depressions thathave very small openings.

One widely used thin film deposition technique is Chemical VaporDeposition (CVD). In a CVD system, one or more precursors that arecapable of reacting to form a solid thin film are mixed in a gas orvapor state, and then the precursor mixture is presented to the surfaceof the workpiece. The surface of the workpiece catalyzes the reactionbetween the precursors to form a thin solid film at the workpiecesurface. The most common way to catalyze the reaction at the surface ofthe workpiece is to heat the workpiece to a temperature that causes thereaction.

Although CVD techniques are useful in many applications, they also haveseveral drawbacks. For example, if the precursors are not highlyreactive, then a high workpiece temperature is needed to achieve areasonable deposition rate. Such high temperatures are not typicallydesirable because heating the workpiece can be detrimental to thestructures and other materials that are already formed on the workpiece.Implanted or doped materials, for example, migrate in the siliconsubstrate when a workpiece is heated. On the other hand, if morereactive precursors are used so that the workpiece temperature can belower, then reactions may occur prematurely in the gas phase beforereaching the substrate. This is not desirable because the film qualityand uniformity may suffer, and also because it limits the types ofprecursors that can be used. Thus, CVD techniques may not be appropriatefor many thin film applications.

Atomic Layer Deposition (ALD) is another thin film deposition techniquethat addresses several of the drawbacks associated with CVD techniques.FIGS. 1A and 1B schematically illustrate the basic operation of ALDprocesses. Referring to FIG. 1A, a layer of gas molecules A_(x) coatsthe surface of a workpiece W. The layer of A_(x) molecules is formed byexposing the workpiece W to a precursor gas containing A_(x) molecules,and then purging the chamber with a purge gas to remove excess A_(x)molecules. This process can form a monolayer of A_(x) molecules on thesurface of the workpiece W because the A_(x) molecules at the surfaceare held in place during the purge cycle by physical adsorption forcesat moderate temperatures or chemisorption forces at higher temperatures.The layer of A_(x) molecules is then exposed to another precursor gascontaining B_(y) molecules. The A_(x) molecules react with the B_(y)molecules to form an extremely thin solid layer of material on theworkpiece W. The chamber is then purged again with a purge gas to removeexcess B_(y) molecules.

FIG. 2 illustrates the stages of one cycle for forming a thin solidlayer using ALD techniques. A typical cycle includes (a) exposing theworkpiece to the first precursor A_(x), (b) purging excess A_(x)molecules, (c) exposing the workpiece to the second precursor B_(y), andthen (d) purging excess B_(y) molecules. In actual processing severalcycles are repeated to build a thin film on a workpiece having thedesired thickness. For example, each cycle may form a layer having athickness of approximately 0.5-1.0 Å, and thus it takes approximately60-120 cycles to form a solid layer having a thickness of approximately60 Å.

FIG. 3 schematically illustrates an ALD reactor 10 having a chamber 20coupled to a gas supply 30 and a vacuum 40. The reactor 10 also includesa heater 50 that supports the workpiece W and a gas dispenser 60 in thechamber 20. The gas dispenser 60 includes a plenum 62 operativelycoupled to the gas supply 30 and a distributor plate 70 having aplurality of holes 72. In operation, the heater 50 heats the workpiece Wto a desired temperature, and the gas supply 30 selectively injects thefirst precursor A_(x), the purge gas, and the second precursor B_(y) asshown above in FIG. 2. The vacuum 40 maintains a negative pressure inthe chamber to draw the gases from the gas dispenser 60 across theworkpiece W and then through an outlet of the chamber 20.

One drawback of ALD processing is that it is difficult to avoid mixingbetween the first and second precursors in the chamber apart from thesurface of the workpiece. For example, a precursor may remain onsurfaces of the gas dispenser or on other surfaces of the chamber evenafter a purge cycle. This results in the unwanted deposition of thesolid material on components of the reaction chamber. The first andsecond precursors may also mix together in a supply line or other areaof a reaction chamber to prematurely form solid particles beforereaching the surface of the workpiece. Thus, the components of the ALDreactor and the timing of the A_(x)/purge/B_(y)/purge pulses of a cycleshould not entrap or otherwise cause mixing of the precursors in amanner that produces unwanted deposits or premature reactions.

Another drawback of ALD processing is that the film thickness may bedifferent at the center of the workpiece than at the periphery. Toovercome this problem, the center of some distributor plates do not haveany holes 72. In practice, however, this may cause the film at thecenter of the workpiece to be thinner than the film at the periphery.Moreover, the center portion of such plates may become coated with thesolid material because it is difficult to purge all of the precursorsfrom this portion of the gas dispenser 60 during normal purge cycles.Therefore, there is a need to resolve the problem of having a differentfilm thickness at the center of the workpiece than at the periphery.

SUMMARY

The present invention is directed toward reactors for deposition ofmaterials onto a micro-device workpiece, systems that include suchreactors, and methods for depositing materials onto micro-deviceworkpieces. In one embodiment, a reactor for depositing a materialcomprises a reaction chamber and a gas distributor that directs gasflows to a workpiece. The reaction chamber can include an inlet and anoutlet, and the gas distributor is positioned in the reaction chamber.The gas distributor has a compartment coupled to the inlet to receive agas flow and a distributor plate including a first surface facing thecompartment, a second surface facing the reaction chamber, and aplurality of passageways. The passageways extend through the distributorplate from the first surface to the second surface. Additionally, atleast one of the passageways has at least a partially occluded flow paththrough the plate. For example, the occluded passageway can be canted atan oblique angle relative to the first surface of the distributor plateso that gas flowing through the canted passageway changes direction asit passes through the distributor plate.

The compartment of the gas distributor can be defined by a sidewall, andthe distributor plate can extend transverse relative to the sidewall. Inone embodiment, the distributor plate has an inner region, an outerregion, and a peripheral edge spaced laterally inward from the sidewallto define a gap between the peripheral edge and the sidewall. In otherembodiments, the peripheral edge of the distributor plate can be coupledto the sidewall.

The distributor plate can have several different embodiments. Thedistributor plate, for example, can have a first plurality ofpassageways in the inner region that are canted at an oblique anglerelative to the first surface of the distributor plate, and a secondplurality of passageways in the outer region that are generally normalto the first surface of the distributor plate. In another embodiment,all of the passageways through the distributor plate can be canted at anangle. The size of the passageways can also vary across the distributorplate. In one embodiment, a first plurality of passageways in the innerregion have a cross-sectional dimension of approximately 0.01-0.07 inch,and a second plurality of passageways in the outer region have across-sectional dimension of approximately 0.08-0.20 inch. In stillother embodiments, a first plurality of passageways in the inner regionare canted at a first oblique angle relative to the first surface of thedistributor plate, and a second plurality of passageways in the outerregion are canted at a second oblique angle relative to the firstsurface of the distributor plate. The canted passageways are generallyangled downward and radially outward from the first surface to thesecond surface to direct the gas flow radially outward across thesurface of the workpiece. For example, the canted passageways can extendat an angle of approximately 15 degrees to approximately 85 degreesrelative to the first surface of the distributor plate. The passageways,however, can be angled at different angles or canted in differentdirections in other embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are schematic cross-sectional views of stages in atomiclayer deposition processing in accordance with the prior art.

FIG. 2 is a graph illustrating a cycle for forming a layer using atomiclayer deposition in accordance with the prior art.

FIG. 3 is a schematic representation of a system including a reactor forvapor deposition of a material onto a microelectronic workpiece inaccordance with the prior art.

FIG. 4 is a schematic representation of a system having a reactor fordepositing a material onto a micro-device workpiece in accordance withone embodiment of the invention.

FIG. 5 is an isometric, cross-sectional view illustrating a portion of areactor for depositing a material onto a micro-device workpiece inaccordance with an embodiment of the invention.

FIG. 6 is a cross-sectional view of a reactor for depositing a materialonto a micro-device workpiece in accordance with another embodiment ofthe invention.

FIG. 7 is a partial cross-sectional view of a distributor plate for usein a reactor for depositing a material onto a micro-device workpiece inaccordance with another embodiment of the invention.

FIG. 8 is a schematic representation of a system including a reactor fordepositing a material onto a micro-device workpiece in accordance withanother embodiment of the invention.

DETAILED DESCRIPTION

The following disclosure is directed toward reactors for depositing amaterial onto a micro-device workpiece, systems including such reactors,and methods for depositing a material onto a micro-device workpiece.Many specific details of the invention are described below withreference to depositing materials onto micro-device workpieces. The term“micro-device workpiece” is used throughout to include substrates uponwhich and/or in which microelectronic devices, micromechanical devices,data storage elements, and other features are fabricated. For example,micro-device workpieces can be semiconductor wafers, glass substrates,insulative substrates, and many other types of materials. The term “gas”is used throughout to include any form of matter that has no fixed shapeand will conform in volume to the space available, which specificallyincludes vapors (i.e., a gas having a temperature less than the criticaltemperature so that it may be liquified or solidified by compression ata constant temperature). Additionally, several aspects of the inventionare described with respect to Atomic Layer Deposition (“ALD”), butcertain aspects may be applicable to other types of depositionprocesses. Several embodiments in accordance with the invention are setforth in FIGS. 4-8 and the related text to provide a thoroughunderstanding of particular embodiments of the invention. A personskilled in the art will understand, however, that the invention may haveadditional embodiments, or that the invention may be practiced withoutseveral of the details in the embodiments shown in FIGS. 4-8.

A. Deposition Systems

FIG. 4 is a schematic representation of a system 100 for depositing amaterial onto a micro-device workpiece W in accordance with anembodiment of the invention. In this embodiment, the system 100 includesa reactor 110 having a reaction chamber 120 coupled to a gas supply 130and a vacuum 140. For example, the reaction chamber 120 can have aninlet 122 coupled to the gas supply 130 and an outlet 124 coupled to thevacuum 140.

The gas supply 130 includes a plurality of gas sources 132 (identifiedindividually as 132 a-c), a valve assembly 133 having a plurality ofvalves 134 (identified individually as 134 a-c), and a plurality of gaslines 136 and 137. The gas sources 132 can include a first gas source132 a for providing a first precursor gas “A,” a second gas source 132 bfor providing a second precursor gas “B,” and a third gas source 132 cfor providing a purge gas P. The first and second precursors A and B canbe the constituents that react to form the thin, solid layer on theworkpiece W. The p-urge gas P can a type of gas that is compatible withthe reaction chamber 120 and the workpiece W. The first gas source 132 ais coupled to a first valve 134 a, the second gas source 132 b iscoupled to a second valve 134 b, and the third gas source 132 c iscoupled to a third valve 134 c. The valves 134 a-c are operated by acontroller 142 that generates signals for pulsing the individual gasesthrough the reaction chamber 120 in a number of cycles. Each cycle caninclude a first pulse of the first precursor A, a second pulse of thepurge gas, a third pulse of the second precursor B, and a fourth pulseof the purge gas.

The reactor 110 in the embodiment illustrated in FIG. 4 also includes aworkpiece support 150 and a gas distributor 160 in the reaction chamber120. The workpiece support 150 can be a plate having a heating elementto heat the workpiece W to a desired temperature for catalyzing thereaction between the first precursor A and the second precursor B at thesurface of the workpiece W. The workpiece support 150, however, may notbe heated in all applications.

The gas distributor 160 is positioned at the inlet 122 of the reactionchamber 120. The gas distributor 160 has a compartment or plenum 162that is defined, at least in part, by a sidewall 164. The compartment orplenum 162 can be further defined by a chamber lid 166. The gasdistributor 160 further includes a distributor plate 170 having a firstsurface 171 a facing the compartment 162, a second surface 171 b facingaway from the compartment 162, and a plurality of passageways 172(identified by reference numbers 172 a and 172 b). As explained in moredetail below, a gas flow F in the compartment 162 flows through thepassageways 172 a-b and through a gap 180 between the sidewall 164 andthe distributor plate 170. As explained in more detail below, thisparticular embodiment of the distributor plate 170 performs thefollowing functions: (a) directs the gas flow F to provide a moreuniform film thickness across the workpiece W; and (b) limits areas inthe reaction chamber where the precursors can adduct and mix prematurelybefore contacting the workpiece.

B. Gas Distributors and Distributor Plates

FIG. 5 illustrates a particular embodiment of the gas distributor 160and the distributor plate 170 in greater detail. In this embodiment, thedistributor plate 170 has an inner region 173 a with a first pluralityof passageways 172 a and an outer region 173 b with a second pluralityof passageways 172 b. The first passageways 172 a extend from the firstsurface 171 a to the second surface 171 b, and at least a portion ofeach of the first passageways 172 a is at least partially occluded alonga flow path to the plate 170. In this particular embodiment, the firstpassageways 172 a are occluded by being canted at an oblique anglerelative to the first surface 171 a and/or the plane defined by theplate 170. The term “occluded,” as used herein, is not limited to anobstruction that blocks the passageways 172, but rather means that someof the gas molecules flowing through the first passageways 172 a cannotflow through the plate 170 along a direct “line-of-sight” between thefirst surface 171 a and the second surface 171 b normal to the planedefined by the plate 170. It will be appreciated that canting the firstpassageways 172 a at an oblique angle relative to the plate 170 caneither fully or at least partially block the direct line-of-sight to theworkpiece while still allowing gas to flow through the first passageways172 a. The first passageways 172 a can be canted at an angle ofapproximately 15° to approximately 85° relative to the plane defined bythe plate 170. The second passageways 172 b extend through the plate 170generally normal to the first surface 171 a such that they provide adirect line-of-sight to the workpiece throughout the fullcross-sectional dimension of the second passageways 172 b. The secondpassageways 172 b can also have bevels 176 at the first surface 171 aand/or the second surface 171 b.

The distributor plate 170 is carried by a number of retainers 177 thatare coupled to the lid 166 or another component of the reaction chamber120. The retainers 177 are brackets, posts, or other suitable devicesthat can hold the distributor plate 170 relative to the inlet 122 andthe sidewall 164. In this embodiment, the distributor plate 170 has aperipheral edge 175 spaced apart from the sidewall 164 by an annular gap180. In operation, therefore, the gas flow F has a first component F₁that flows through the first passageways 172 a, a second component F₂that flows through the second passageways 172 b, and a third componentF₃ that flows through the gap 180. The first passageways 172 a directthe first flow component F₁ downward and radially outward to preventover-saturating the center portion of the workpiece with the precursors.The second passageways 172 b direct the second flow component F₂downward and generally normal to the plate 170 to provide more gasmolecules to an outer region of the workpiece. The gap 180 also providesan enhanced flow of gas at the outer and peripheral regions of theworkpiece.

Several embodiments of the distributor plate 170 are accordinglyexpected to provide more uniform saturation of the workpiece W with thefirst and second precursors A and B to provide a more uniform layer ofmaterial on the workpiece. Additionally, because the inner region 173 aof the plate 170 includes the first plurality of passageways 172 a, thesurface areas upon which the first and second precursors A and B canadduct is reduced compared to conventional plates that do not have anyopenings in the inner region. This is expected to reduce the build up ofthe deposited material on the first surface 171 a of the distributorplate 170. It is also expected that such a reduction in the surface areawill enhance the ability to control the uniformity of the depositedlayer and the endpoints of the gas pulses for better quality depositionsand enhanced throughput.

The first passageways 172 a can also have a different cross-sectionaldimension than the second passageways 172 b as shown in the particularembodiment illustrated in FIG. 5. The first passageways, for example,can have openings of approximately 0.01-0.07 inch, and the secondpassageways 172 b can have openings of approximately 0.08-0.20 inch. Ina particular embodiment, the first passageways 172 a at the inner region173 a have a circular opening with a diameter of approximately 0.03inch, and the second passageways 172 b in the outer region 173 b have acircular opening with a diameter of approximately 0.10 inch. It will beappreciated that the cross-sectional size of the first and secondpassageways 172 a-b can be the same, or that they can havecross-sectional dimensions that are different than the ranges set forthabove.

The passageways 172 can accordingly be configured to further enhance orrestrict the gas flow to particular areas of the workpiece by canting,or otherwise occluding selected passageways, and/or varying the sizes ofthe cross-sectional dimensions of the passageways. In the embodimentshown in FIG. 5, for example, the smaller cross-sectional dimension ofthe first passageways 172 a inhibits gas molecules from contacting thecentral region of the workpiece W, and the larger cross-sectionaldimension of the second passageways 172 b enhances the number of gasmolecules that contact the outer region of the workpiece. Therefore, thecross-sectional dimensions and the angles of inclination of thepassageways can be used either separately or together to provide thedesired distribution of gas to the surface of the workpiece.

FIG. 6 is a cross-sectional view of a distributor plate 670 inaccordance with another embodiment of the invention. Several componentsof the distributor plate 670 are the same as the distributor plate 170,and thus like reference numbers refer to like components in FIGS. 4-6.The distributor plate 670 can include a plurality of passageways 172that are canted at an oblique angle relative to the plane defined by theplate 670. In this embodiment, all of the passageways 172 are canted atthe same angle. The angle of inclination can be approximately 15 degreesto approximately 85 degrees. In operation, the embodiment of thedistributor plate 670 shown in FIG. 6 has a first flow component F₁ thatflows radially outwardly and downward from the plate 670, and a secondflow component F₂ that flows through the gap 180. The passageways 172can have the same cross-sectional dimensions, or they can have differentcross-sectional dimensions similar to the plate 170 described above.

FIG. 7 is a partial cross-sectional view of a distributor plate 770 inaccordance with another embodiment of the invention. The distributorplate 770 is similar to the distributor plate 170, and thus likereference numbers refer to like components in FIGS. 4, 5 and 7. In thisembodiment, the first passageways 172 a at the inner region 173 a arecanted at a first angle α, and the second passageways 172 b in thesecond region 173 b are canted at a second angle β. The angle α isgenerally less than the angle 62 relative to the plane P-P defined bythe plate 770. As such, the first passageways 172 a have a firstocclusion area A₁ in which there is no direct line-of-sight through theplate 770 to the workpiece W along a path normal to the plate 170. Thesecond passageways 172 b, however, have a smaller occlusion area A₂because the higher angle β allows gas to pass completely through aportion of the second passageways 172 b along a path normal to the plate770 or the workpiece W. By increasing the size of the occlusion area A,for the first passageways 172 a relative to the occlusion area A₂ forthe second passageways 172 b, fewer gas molecules are likely to bedeposited on the central region C of the workpiece W. It will beappreciated that the distributor plate 770 can have variable canting ofthe passageways 172 from the center to the perimeter of the plate alonga continuum or throughout several regions in which the angle of inclineincreases toward the periphery of the plate 770. Accordingly, in otherembodiments, the distributor plate 770 can have more than two regions inwhich the passageways are canted at different angles.

C. Additional Deposition Systems

FIG. 8 is a schematic illustration of another embodiment of a system 800for depositing a material onto a microelectronic workpiece. The system800 is similar to the system 100, and thus like reference numbers referto like components in FIGS. 4 and 8. The difference between the system800 and the system 100 is that the system 800 includes a gas distributor860 with a distributor plate 870 that extends to the sidewall 164 toeliminate the gap 180 shown in FIG. 4. It will be appreciated that thedistributor plate 870 can include any of the distributor platesexplained above with reference to FIGS. 4-7. Therefore, other aspects ofthe invention include a completely enclosed compartment or plenum 862.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thespirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1-62. (Canceled)
 63. A method for forming a thin layer on a micro-deviceworkpiece, comprising: providing a flow of gas to a gas distributorhaving a distributor plate with an inner region and an outer region;passing a first portion of the gas flow through the inner region of theplate along a path extending at an oblique angle relative to a planedefined by the plate such that the first portion of the gas exits theplate having a first flow characteristic; and flowing a second portionof the gas flow through the outer region of the plate such that thesecond portion of the gas exits the plate having a second flowcharacteristic different than the first flow characteristic.
 64. Themethod of claim 63 wherein flowing the second portion of the gas throughthe outer region of the plate comprises dispensing the second portion ofthe gas at an angle that is at least substantially normal to the planedefined by the plate.
 65. The method of claim 63 wherein passing thefirst portion of the gas through the inner region of the plate comprisesdispensing the first portion of the gas at an angle that is obliquerelative to the plane defined by the plate.
 66. The method of claim 63wherein: flowing the second portion of the gas through the outer regionof the plate comprises dispensing the second portion of the gas at anangle that is at least substantially normal to the plane defined by theplate; and passing the first portion of the gas through the inner regionof the plate comprises dispensing the first portion of the gas at anangle that is oblique relative to the plane defined by the plate. 67.The method of claim 63 wherein flowing the second portion of the gasthrough the outer region of the plate comprises dispensing the secondportion of the gas at an angle that is oblique relative to the planedefined by the plate.
 68. The method of claim 63 wherein passing thefirst portion of the gas through the inner region of the plate comprisesdispensing the first portion of the gas at an angle of approximately 15°to approximately 85° relative to the plane defined by the plate.
 69. Themethod of claim 63 wherein: flowing the second portion of the gasthrough the outer region of the plate comprises dispensing the secondportion of the gas at an oblique angle α relative to the plane definedby the plate; and passing the first portion of the gas through the innerregion of the plate comprises dispensing the first portion of the gas atan oblique angle β relative to the plane defined by the plate differentthan the angle α.
 70. The method of claim 63 wherein: flowing the secondportion of the gas through the outer region of the plate comprisesdispensing the second portion of the gas at an oblique angle α relativeto the plane defined by the plate; and passing the first portion of thegas through the inner region of the plate comprises dispensing the firstportion of the gas at the oblique angle α relative to the plane definedby the plate.
 71. The method of claim 63, further comprising directing aportion of the gas flow through a gap between a peripheral portion ofthe distributor plate and a sidewall.
 72. A method for forming a thinlayer on a micro-device workpiece, comprising: providing a flow of gasto a gas distributor having a distributor plate with an inner region andan outer region; restricting a portion of the gas flow from passingthrough a plurality of first passageways at the inner region of thedistributor plate; passing another portion of the gas flow through aplurality of second passageways at the outer region of the distributorplate; and flowing still another portion of the gas flow through a gaparound a peripheral edge of the distributor plate.